From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id ABC06C433DF for ; Tue, 30 Jun 2020 17:39:57 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7EFE920842 for ; Tue, 30 Jun 2020 17:39:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="WH6VEKe8"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="NSObXOKq" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7EFE920842 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To:Message-Id:Date: Subject:To:From:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=iwqF7Cg8ps5cgvqWPLQrMNJ2wmqKsdna9DXzv3il6jk=; b=WH6VEKe8xPe8Poeys3Oe/HYNx ehugYrvFyEVQOBqeDGSZHgo0Rlqmd2hzauaLweTOEOjgWaeQsRPxbf/RHmul/8v6PT6ulgRsAq1fn U2/AOgZLu8RUB8OyBMTnJv6PfP62cgShfI8lXc4ZU137do8wJJ25nl9ho5tvEsTUfOSXSIPgwySoT n8EnJctr9IK1H7AhdzJuncQ4+X0ahTfh57Zcl5eMWvBM2dVYujX53AYethDGe4egREnCHz5xvz3Kf 5YOc59g6EaHGlL0PeRlxWXj7IPy9x0mVdcek1TUCGtw8Bys5DsRwdXdQbdLzkSBtDr2XW1i6c9A7G 9NsyBaIlw==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jqKD1-0001Aw-Qm; Tue, 30 Jun 2020 17:38:15 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jqKCo-000151-Dh for linux-arm-kernel@lists.infradead.org; Tue, 30 Jun 2020 17:38:05 +0000 Received: from localhost.localdomain (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 169692078D; Tue, 30 Jun 2020 17:37:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593538681; bh=pesny1RdH7DbGb79H7QfthXwHtI2vIe4lfYhnipzWT0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NSObXOKqu4DQj3yJ/Fya2llNNcBmFi2aQ4hG3Eviqhclj+MeUmz+5cI5F3VnY54w/ DU6VQ9WPF9wMbLSnDQan0OVflp98HStaZgU3JeA8wiO47q1ZwVbBRwu6UF1at5VxEm 2M85sCNpJOz4yx/ilpz0JRysnZ/Ae1xykmJe1+dU= From: Will Deacon To: linux-kernel@vger.kernel.org Subject: [PATCH 04/18] alpha: Override READ_ONCE() with barriered implementation Date: Tue, 30 Jun 2020 18:37:20 +0100 Message-Id: <20200630173734.14057-5-will@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200630173734.14057-1-will@kernel.org> References: <20200630173734.14057-1-will@kernel.org> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200630_133802_686167_FF790079 X-CRM114-Status: GOOD ( 22.74 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , "Michael S. Tsirkin" , Peter Zijlstra , Catalin Marinas , Jason Wang , virtualization@lists.linux-foundation.org, Will Deacon , Arnd Bergmann , Alan Stern , Sami Tolvanen , Matt Turner , kernel-team@android.com, Marco Elver , Kees Cook , "Paul E. McKenney" , Boqun Feng , Josh Triplett , Ivan Kokshaysky , linux-arm-kernel@lists.infradead.org, Richard Henderson , Nick Desaulniers , linux-alpha@vger.kernel.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Rather then relying on the core code to use smp_read_barrier_depends() as part of the READ_ONCE() definition, instead override __READ_ONCE() in the Alpha code so that it is treated the same way as smp_load_acquire(). Acked-by: Paul E. McKenney Signed-off-by: Will Deacon --- arch/alpha/include/asm/barrier.h | 61 ++++---------------------------- arch/alpha/include/asm/rwonce.h | 19 ++++++++++ 2 files changed, 26 insertions(+), 54 deletions(-) create mode 100644 arch/alpha/include/asm/rwonce.h diff --git a/arch/alpha/include/asm/barrier.h b/arch/alpha/include/asm/barrier.h index 92ec486a4f9e..2ecd068d91d1 100644 --- a/arch/alpha/include/asm/barrier.h +++ b/arch/alpha/include/asm/barrier.h @@ -2,64 +2,17 @@ #ifndef __BARRIER_H #define __BARRIER_H -#include - #define mb() __asm__ __volatile__("mb": : :"memory") #define rmb() __asm__ __volatile__("mb": : :"memory") #define wmb() __asm__ __volatile__("wmb": : :"memory") -/** - * read_barrier_depends - Flush all pending reads that subsequents reads - * depend on. - * - * No data-dependent reads from memory-like regions are ever reordered - * over this barrier. All reads preceding this primitive are guaranteed - * to access memory (but not necessarily other CPUs' caches) before any - * reads following this primitive that depend on the data return by - * any of the preceding reads. This primitive is much lighter weight than - * rmb() on most CPUs, and is never heavier weight than is - * rmb(). - * - * These ordering constraints are respected by both the local CPU - * and the compiler. - * - * Ordering is not guaranteed by anything other than these primitives, - * not even by data dependencies. See the documentation for - * memory_barrier() for examples and URLs to more information. - * - * For example, the following code would force ordering (the initial - * value of "a" is zero, "b" is one, and "p" is "&a"): - * - * - * CPU 0 CPU 1 - * - * b = 2; - * memory_barrier(); - * p = &b; q = p; - * read_barrier_depends(); - * d = *q; - * - * - * because the read of "*q" depends on the read of "p" and these - * two reads are separated by a read_barrier_depends(). However, - * the following code, with the same initial values for "a" and "b": - * - * - * CPU 0 CPU 1 - * - * a = 2; - * memory_barrier(); - * b = 3; y = b; - * read_barrier_depends(); - * x = a; - * - * - * does not enforce ordering, since there is no data dependency between - * the read of "a" and the read of "b". Therefore, on some CPUs, such - * as Alpha, "y" could be set to 3 and "x" to 0. Use rmb() - * in cases like this where there are no data dependencies. - */ -#define read_barrier_depends() __asm__ __volatile__("mb": : :"memory") +#define __smp_load_acquire(p) \ +({ \ + __unqual_scalar_typeof(*p) ___p1 = \ + (*(volatile typeof(___p1) *)(p)); \ + compiletime_assert_atomic_type(*p); \ + ___p1; \ +}) #ifdef CONFIG_SMP #define __ASM_SMP_MB "\tmb\n" diff --git a/arch/alpha/include/asm/rwonce.h b/arch/alpha/include/asm/rwonce.h new file mode 100644 index 000000000000..83a92e49a615 --- /dev/null +++ b/arch/alpha/include/asm/rwonce.h @@ -0,0 +1,19 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright (C) 2019 Google LLC. + */ +#ifndef __ASM_RWONCE_H +#define __ASM_RWONCE_H + +#include + +/* + * Alpha is apparently daft enough to reorder address-dependent loads + * on some CPU implementations. Knock some common sense into it with + * a memory barrier in READ_ONCE(). + */ +#define __READ_ONCE(x) __smp_load_acquire(&(x)) + +#include + +#endif /* __ASM_RWONCE_H */ -- 2.27.0.212.ge8ba1cc988-goog _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel